Effect of Driving Frequency on the EL Characteristics of Thick Ceramic Insulating Type TFEL Devices Using Y_2O_3-Based Phosphor Emitting Layer

摘要

The driving frequency dependence of EL characteristics were investigated in thick ceramic insulating type thin-film electroluminescent (TFEL) devices with various Mn-activated Y_2O_3-based phosphor thin-film emitting layers driven by a sinusoidal wave voltage. High luminous efficiencies of approximately 10 and 1 lm/W were obtained in the TFEL devices driven at 60 Hz and 1 kHz, respectively. The difference in luminous efficiency was mainly caused by the increase of input power in 1 kHz-driven-devices resulting from a dielectric loss of a thick BaTiO_3 ceramic sheet used as the insulating layer. The correlation between the sound emission from the devices and the effective power consumed in the devices was found with variations in both the applied voltage and the frequency. The higher input power of the 1 kHz-driven-device may be attributable to sound emissions resulting from the piezo-electricity of BaTiO_3 ceramics.